The governor of New Jersey on Saturday issued a stay-at-home order for nearly all of the state’s 9 million residents in the fight against the spread of the coronavirus.

Similar sweeping mandates have been made in California, Illinois, New York and Pennsylvania.

“We must flatten the curve and ensure residents are practicing social distancing,” New Jersey Gov. Phil Murphy said in announcing the new restrictions. But, he added, “Even with this order in effect … life in New Jersey does not have to come to a complete standstill.”

The governor told residents not to panic, but, he said, “We’re at war.”

Starting at 9 p.m. Saturday, New Jersey residents must stay home and all nonessential businesses have to close indefinitely. All gatherings including weddings, in-person services and parties, are canceled until further notice, Murphy said.

Businesses considered essential that can remain open include grocery stores and pharmacies, gas stations, banks and other financial institutions and laundromats.

Employees who must report to work are encouraged to get a letter from their job indicating that they work in an “industry permitted to continue operations,” according to the state’s newly launched coronavirus website.

New Jersey had 1,327 confirmed coronavirus cases as of Saturday with 442 new positive test results since Friday. The state has had 16 deaths.

“We mourn the tragic loss of life,” the governor said.

But, he said, “The increase in the positive test results is completely expected” due to the state’s aggressive testing.

The more information the state has the better able it is to “break the back of this virus,” Murphy said.

New Jersey’s announcement comes after Illinois Gov. J.B. Pritzker on Friday ordered his state’s nearly 13 million residents to stay home. He said at a press conference that he did not come to the decision easily.

“I fully recognize that in some cases, I am choosing between saving people’s lives and saving people’s livelihood,” he said. “But ultimately you can’t have a livelihood if you don’t have your life.”

Pritzker said residents will be able to leave their homes to buy food, or pick up a prescription at the pharmacy and can go out for a walk.

He said the goal of the stay-at-home order is for people to maintain social distancing and for those who have already taken precautions their lives “will not change very much.” The order is expected to become effective Saturday evening and will remain in place until April 7 but could go longer, Pritzker said.

Also on Friday, New York Gov. Andrew Cuomo ordered all nonessential businesses to cease operating outside the home and put new requirements in place for people over 70 or with underlying health conditions to avoid public transportation and stay home except for solitary exercise.

The requirements also urge New Yorkers to practice social distancing and to stay in their homes as much as possible.

“Your actions can affect my health, that is where we are,” Cuomo said at a press conference.

Coronavirus cases in New York surged to more than 10,000 with 6,211 cases in New York City alone, Cuomo said Saturday. According to the governor, cases are slowing in Westchester County but are growing on Long Island.

California Gov. Gavin Newsom also issued such an order, which went into effect Thursday night and will remain in place until further notice. It says residents should leave their homes only when necessary.

In Pennsylvania, Gov. Tom Wolf ordered that all businesses that are not “life-sustaining” close.